I'm in California, home of the BIG folder. I dream of using two slabs of aluminum to do grips on a mutilated folder using an Ontario Black Wind Katana blade with most of the grip lopped off.
There's another way of getting a monster sub-4" blade combat folder: the Muskrat concept. A Muskrat is a two-locking-blade knife rigged "back to back", so you're doing both a forward-grip and reverse-grip hold. Potent with practice, and seriously intimidating. And legally there ain't squat they can do about it.
Rob, my understanding is that in a "good gun law state" like TN, it's highly unusual for the cops to still care about knife blade length limits once you've got a gun carry permit with background check, etc. True? Probably a "depends on the cop" thing?